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>Impact of Synoptic Wind Intensification and Relaxation on the Dynamics and Heat Budget of the South Senegalese Upwelling Sector
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Impact of Synoptic Wind Intensification and Relaxation on the Dynamics and Heat Budget of the South Senegalese Upwelling Sector
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机译：Impact of Synoptic Wind Intensification and Relaxation on the Dynamics and Heat Budget of the South Senegalese Upwelling Sector
In addition to their well-known seasonal cycle, eastern boundary upwelling systems (EBUS) undergo mod-ulation on shorter synoptic to intraseasonal time scales. Energetic intensifications and relaxations of upwelling-favorable winds with 5-10-day typical time scales can impact the EBUS dynamics and biogeochemical functioning. In this work the dynamical effects of wind-forced synoptic fluctuations on the South Senegalese Upwelling Sector (SSUS) are characterized. The region geomorphology is unique with its wide continental shelf and a major coastline discontinuity at its northern edge. The ocean response to synoptic events is explored using a modeling framework that involves applying idealized syn-optic wind intensification or relaxation to a five-member climatological SSUS ensemble run. Model evaluation against sparse midshelf in situ observations indicates qualitative agreement in terms of synoptic variability of temperature, stratifi-cation, and ocean currents, despite a moderate but systematic bias in current intensity. Modeled synoptic wind and heat flux fluctuations produce clear modulations of all dynamical variables with robust SSUS-scale and mesoscale spatial pat-terns. A mixed layer heat budget analysis is performed over the continental shelf to uncover the dominant processes in-volved in SSUS synoptic variability. Modulations of horizontal advection and atmospheric forcing are the leading-order drivers of heat changes during either wind intensification or relaxation while vertical dynamics is of primary importance only in a very localized area. Also, modest asymmetries in the oceanic responses to upwelling intensification and relaxation are only identified for meridional velocities. This brings partial support to the hypothesis that synoptic variability has a modest net effect on the climatological state and functioning of upwelling systems dynamics.
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